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Enabling runtime power management early in analogix_dp_bind() causes following kernel NULL pointer dereference: Unable to handle kernel NULL pointer dereference at virtual address 000007d8 pgd = 28ffa2e4 [000007d8] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT SMP ARM Modules linked in: CPU: 6 PID: 69 Comm: kworker/6:1 Not tainted 4.16.0-rc1-00062-ge25751974ba8 #3622 Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) Workqueue: events deferred_probe_work_func PC is at analogix_dp_resume+0x8/0xc0 LR is at pm_generic_runtime_resume+0x2c/0x38 pc : [<c0531b98>] lr : [<c0543fec>] psr: a0000113 sp : ee13fbd8 ip : 0000001a fp : 00000001 r10: ee0eb080 r9 : c0552bd8 r8 : c0fb1d98 r7 : eebb1010 r6 : eeae9808 r5 : 00000000 r4 : d4850415 r3 : ee0ed010 r2 : b2d05e00 r1 : 00000000 r0 : 00000000 Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 2000406a DAC: 00000051 Process kworker/6:1 (pid: 69, stack limit = 0x913205b4) Stack: (0xee13fbd8 to 0xee140000) ... [<c0531b98>] (analogix_dp_resume) from [<c0543fec>] (pm_generic_runtime_resume+0x2c/0x38) [<c0543fec>] (pm_generic_runtime_resume) from [<c054ffb4>] (__genpd_runtime_resume+0x2c/0x8c) [<c054ffb4>] (__genpd_runtime_resume) from [<c0552d24>] (genpd_runtime_resume+0x14c/0x258) [<c0552d24>] (genpd_runtime_resume) from [<c0547798>] (__rpm_callback+0x134/0x214) [<c0547798>] (__rpm_callback) from [<c0547898>] (rpm_callback+0x20/0x80) [<c0547898>] (rpm_callback) from [<c0546ff4>] (rpm_resume+0x3a0/0x734) [<c0546ff4>] (rpm_resume) from [<c05475ec>] (__pm_runtime_resume+0x64/0x9c) [<c05475ec>] (__pm_runtime_resume) from [<c053b95c>] (__device_attach+0x8c/0x134) [<c053b95c>] (__device_attach) from [<c053ad08>] (bus_probe_device+0x88/0x90) [<c053ad08>] (bus_probe_device) from [<c05390d0>] (device_add+0x3a8/0x580) [<c05390d0>] (device_add) from [<c06764c4>] (i2c_register_adapter+0xd4/0x3ec) [<c06764c4>] (i2c_register_adapter) from [<c05321c8>] (analogix_dp_bind+0x2a0/0x410) [<c05321c8>] (analogix_dp_bind) from [<c0528e90>] (exynos_dp_bind+0x9c/0x12c) [<c0528e90>] (exynos_dp_bind) from [<c0535bc4>] (component_bind_all+0xfc/0x258) [<c0535bc4>] (component_bind_all) from [<c0522ee8>] (exynos_drm_bind+0x15c/0x28c) [<c0522ee8>] (exynos_drm_bind) from [<c0536378>] (try_to_bring_up_master+0x1b8/0x29c) [<c0536378>] (try_to_bring_up_master) from [<c05364fc>] (component_add+0xa0/0x170) [<c05364fc>] (component_add) from [<c0528fe4>] (exynos_dp_probe+0x64/0xb8) [<c0528fe4>] (exynos_dp_probe) from [<c053debc>] (platform_drv_probe+0x50/0xb0) [<c053debc>] (platform_drv_probe) from [<c053bd18>] (driver_probe_device+0x2b8/0x4a0) [<c053bd18>] (driver_probe_device) from [<c0539e4c>] (bus_for_each_drv+0x44/0x8c) [<c0539e4c>] (bus_for_each_drv) from [<c053b970>] (__device_attach+0xa0/0x134) [<c053b970>] (__device_attach) from [<c053ad08>] (bus_probe_device+0x88/0x90) [<c053ad08>] (bus_probe_device) from [<c053b258>] (deferred_probe_work_func+0x3c/0x168) [<c053b258>] (deferred_probe_work_func) from [<c014352c>] (process_one_work+0x1d0/0x7bc) [<c014352c>] (process_one_work) from [<c0143b84>] (worker_thread+0x34/0x4dc) [<c0143b84>] (worker_thread) from [<c014a30c>] (kthread+0x128/0x164) [<c014a30c>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20) Exception stack(0xee13ffb0 to 0xee13fff8) ffa0: 00000000 00000000 00000000 00000000 ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 Code: e2800e37 eafee601 e92d4070 e1a05000 (e59067d8) ---[ end trace bf6046013df7cab2 ]--- This oops happens, because analogix_dp_bind() calls drm_dp_aux_register() which registers i2c adapter. I2C core tries to runtime get i2c host device during registration. This ends in analogix_dp_resume(), but dp context is NULL there. dp context is set in exynos_dp_bind() after executing analogix_dp_bind(). Fix this issue by postponing enabling runtime power management after drm_dp_aux_register(). Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Tested-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Heiko Stuebner <heiko@sntech.de> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180305085741.18896-3-m.szyprowski@samsung.com |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.